/*
 * Copyright (c) 2007-2012, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
/*
 * Copyright 1999-2004 The Apache Software Foundation.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/*
 * $Id: Function.java,v 1.2.4.1 2005/09/14 20:18:43 jeffsuttor Exp $
 */
package com.sun.org.apache.xpath.internal.functions;

import com.sun.org.apache.xalan.internal.res.XSLMessages;
import com.sun.org.apache.xpath.internal.Expression;
import com.sun.org.apache.xpath.internal.ExpressionOwner;
import com.sun.org.apache.xpath.internal.XPathContext;
import com.sun.org.apache.xpath.internal.XPathVisitor;
import com.sun.org.apache.xpath.internal.compiler.Compiler;
import com.sun.org.apache.xpath.internal.objects.XObject;

/**
 * This is a superclass of all XPath functions.  This allows two
 * ways for the class to be called. One method is that the
 * super class processes the arguments and hands the results to
 * the derived class, the other method is that the derived
 * class may process it's own arguments, which is faster since
 * the arguments don't have to be added to an array, but causes
 * a larger code footprint.
 * @xsl.usage advanced
 */
public abstract class Function extends Expression {
    static final long serialVersionUID = 6927661240854599768L;

    /**
     * Set an argument expression for a function.  This method is called by the
     * XPath compiler.
     *
     * @param arg non-null expression that represents the argument.
     * @param argNum The argument number index.
     *
     * @throws WrongNumberArgsException If the argNum parameter is beyond what
     * is specified for this function.
     */
    public void setArg(Expression arg, int argNum) throws WrongNumberArgsException {
        // throw new WrongNumberArgsException(XSLMessages.createXPATHMessage("zero", null));
        reportWrongNumberArgs();
    }

    /**
     * Check that the number of arguments passed to this function is correct.
     * This method is meant to be overloaded by derived classes, to check for
     * the number of arguments for a specific function type.  This method is
     * called by the compiler for static number of arguments checking.
     *
     * @param argNum The number of arguments that is being passed to the function.
     *
     * @throws WrongNumberArgsException
     */
    public void checkNumberArgs(int argNum) throws WrongNumberArgsException {
        if (argNum != 0)
            reportWrongNumberArgs();
    }

    /**
     * Constructs and throws a WrongNumberArgException with the appropriate
     * message for this function object.  This method is meant to be overloaded
     * by derived classes so that the message will be as specific as possible.
     *
     * @throws WrongNumberArgsException
     */
    protected void reportWrongNumberArgs() throws WrongNumberArgsException {
        throw new WrongNumberArgsException(XSLMessages.createXPATHMessage("zero", null));
    }

    /**
     * Execute an XPath function object.  The function must return
     * a valid object.
     * @param xctxt The execution current context.
     * @return A valid XObject.
     *
     * @throws javax.xml.transform.TransformerException
     */
    public XObject execute(XPathContext xctxt) throws javax.xml.transform.TransformerException {

        // Programmer's assert.  (And, no, I don't want the method to be abstract).
        System.out.println("Error! Function.execute should not be called!");

        return null;
    }

    /**
     * Call the visitors for the function arguments.
     */
    public void callArgVisitors(XPathVisitor visitor) {
    }

    /**
     * @see com.sun.org.apache.xpath.internal.XPathVisitable#callVisitors(ExpressionOwner, XPathVisitor)
     */
    public void callVisitors(ExpressionOwner owner, XPathVisitor visitor) {
        if (visitor.visitFunction(owner, this)) {
            callArgVisitors(visitor);
        }
    }

    /**
     * @see Expression#deepEquals(Expression)
     */
    public boolean deepEquals(Expression expr) {
        if (!isSameClass(expr))
            return false;

        return true;
    }

    /**
     * This function is currently only being used by Position()
     * and Last(). See respective functions for more detail.
     */
    public void postCompileStep(Compiler compiler) {
        // no default action
    }
}
